The demands on wireless Long Term Evolution (LTE) and LTE advanced networks (referred to generally herein as “LTE networks”) continue to increase due to subscriber demand. In order to keep up with the demand, operators have continued deploying Frequency Division Duplex (FDD) LTE and/or Time Division Duplex (TDD) LTE networks. While FDD LTE networks are more widely implemented than TDD LTE, TDD LTE has been gaining momentum due in part to its flexibility in not requiring a paired wireless communication spectrum, among other advantages. For example, FDD LTE relies on a paired spectrum for operation, one for uplink and the other for downlink.
However, in TDD LTE, the downlink (DL) and uplink (UL) are on the same frequency in which separation occurs in the time domain; thereby separating transmission direction at the subframe level. The UL/DL duplexing is described in detail with respect to 3GPP specification Technical Specification (TS) 36.211 on a time-slicing schedule, illustrated in Table 1 below.
TABLE 1Uplink-Downlink-Downlinkto-UplinkCon-SwitchpointSubframe NumberfigurationPeriodicity012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 ms DSUUUDDDDD410 ms DSUUUDDDDD510 ms DSUDDDDDDD65 msDSUUUDSUUDThe network operator selects the UL/DL (TDD Mode) configuration, e.g., 0 to 6, and applies the selected TDD mode to all eNBs and User Equipments (UEs) in a geographic region. Referring to Table 1, “D” denotes the subframe allocation for the downlink, “U” refers to the subframe allocation for the uplink, e.g., UL time slice, and “S” denotes a special frame. The TDD Mode is typically stored and configured in the baseband unit, and is sent to UEs on the DL control channel for implementation.
A system view of a portion of an existing LTE TDD system 10 is shown in FIG. 1. System 10 includes one or more evolved Node Basestations (eNBs) 12 and one or more user equipments 14 in communication with the one or more eNBs 12 using LTE TDD standards as are known in the art. In particular, eNB 12 includes baseband unit 16 that implements baseband processing functionality such as signal processing, time switching configuration, among other functions known in the art in accordance with LTE TDD standards. Further, eNB12 includes radio unit 18 in communication with baseband unit 16 for performing radio signal based functions such as receiving/transmitting data. In particular, radio unit 18 consists of subsystems including transmitter 20, receiver 22, switch 24, time switch control 26 for transmitting/receiving signals according to LTE TDD standards as are known in the art. Time switch control 26 operates switch 24 according to the time switching configuration stores in baseband unit 16. Radio unit 18 includes radio processing unit 28 for communicating baseband data to/from baseband unit 16 and processing radio frequency signals. UE 14 includes receiver 30, transmitter 32, switch 34 and time switch control 36 for receiving/transmitting signals. UE 14 further includes processing unit for processing receiving signals and signals to be transmitted to eNBs 12.
However, TDD LTE is not without issues. In particular, TDD uplink (UL) interference becomes a severe problem when base stations, i.e., evolved Node Base stations (eNBs) deployments are more condensed within an operator's network and among other networks. During the subframe allocated for the uplink, “U”, subframe, eNB 12 listens for RF signals from intended UEs only. Any interference signal, i.e., signal from other than intended UEs, may become severe noise and degrade network performance. This UL interference signal has become stronger than before because of the close proximity of the eNBs in which the UL interference dramatically degrades TDD data throughput. The UL interference most often occurs when telecommunications equipment malfunctions, when the TDD network is out of synchronization due to TDD modem misconfiguration, or due to timing reference problems.
Existing solutions only go as far as UL interference detection. For example, the UL interference due to neighbor eNB transmission signal leakage is detected by an eNB. In response, the eNB typically shuts down the impacted hardware receiver path for circuit protection and reports the problem to the network management entity. No root cause identification is even attempted by the eNB.
Another existing approach to the problem of UL interference deals with UL interference at the eNB level. This approach is based on the fact that under interference, the throughput performance suffers. This statistical detection relies on the collection of performance information and/or data metrics at the UL path such as carrier to interference plus noise ratio. However, since TDD data throughput performance degradation may be caused by many factors, this approach cannot help identify root causes of the UL interference.
In other words, the current solutions/approaches are able to detect some UL interference events but they fail to determine the cause of the UL interference, thereby leading to a low throughput system with varying recovery times. The negative impacts on revenue and customer satisfaction can be substantial. While performance data can be collected and analyzes offline through the use of proprietary algorithms to try to identify the nature of the UL interference, such a process is time consuming and requires numerous resources.